Radio decoupling system for excessive amplitudes



y 7, 1940- I P. M. HA-FFCKE 2,199,401

RADIO DECOUPLING SYSTEM FOR EXCESSIVE AMPLITUDES Filed Nov. 2, 1957 2Sheefs-Sheet 1 Pl g l 76 antenna INVENTOR PHILIP M. HAFFCKE fan m" #WATTORNEY May 7, 1940- P. M. HAFFCIKE RADIO DECOUPLING SYSTEM FOREXCESSIVE AMPLITUDES Filed Nov. 2, 1937 2 Sheets-Sheet 2 INVENTOR PHILIPM. HAFFCKE BY ATTORNEY Patented May 7, 1940 RADIO'DECOUPLING SYSTEM FOR-EXCESSIVE AMPLITUDES Philip M. Haffcke, Washington, D. 0. ApplicationNovember 2, 1937, Serial No. 172,398

8 Claims. (01. 250-20) (Granted'under the act of March 3, 1883, asamended April 30, 1928; 370 0. G. 757) UNITED STATES {PATENT OFFICE Thisinvention relates to means for progressively decoupling a radio antennafrom the receiving set associated therewith during periods of excessiveamplitudes of incoming energy, to maintain the level of the signal, ascontrasted with prior apparatus wherein the reception is whollyinterrupted during such periods thereby causing a hole in the reception.

Among the objects of this invention are:

To provide means for applying received energy, outside the signalchannel, to diminish the conductance through the signal channel inresponse to excessive amplitudes of received waves;

To provide means whereby the envelope of the excessive amplitudes willbe rendered inefiective while the signal envelope is maintainedsubstantially at its normal level; v

To make such means as above mentioned to be applicable either betweenthe antenna and the first stage of the receiving set or between'tworadio frequency stages of the set.

Other andfurther objects will appear from the ensuing description whenread in'connection with the drawings wherein:

Fig. 1 illustrates the application of my invention between the antennaand the first stage of the set;

Fig. 2 shows the nature of the oscillograph figure when a spark coil wasset into operation adjacent an ordinary receiving set;

Fig. 3 illustrates the oscillograph figure under conditions like thoseof Fig. 2 when the present invention was used in association with thereceiving set;

Fig. 4 discloses the application of the present invention to a circuitfor the reception of code signals. I

The problem of receiving radio signals intelligibly in spite of theinterfering effects of various phenomena frequently called static, andother like disturbances, has long held the attention of workers in thisart and has resulted in numerous proposed solutions that have. been moreor less effective. One of the heretofore proposed methods of effectingthis result is to interrupt completely the transfer of energy throughthe signal channel of the receiving set and thus to eliminateinterfering noises by silencingthe receiver. While this solution hascertain desirable features it is apparent that a complete stoppage ofreception might easily cause omission of a vital part of a signal and Ihave therefore devised the present means for eliminating the disturbingnoisesv without, except in unusual cases, silencing the receiving set.

In Fig. 1 the antenna 5 is'connected to the plate 6 of a vacuum tube 1connected in series between the antenna 5 and the first'stage of thereceiving set 8, whereby all energy transferred from the antenna to theset 8 must pass through tube 1. Likewise, connected to antenna 5 is aradio frequency amplifier 9 havingpreferably two stages of radiofrequency amplification and so operating as to amplifydisproportionately any received energy having an amplitude above apredetermined limiting value, as set forth in my copending application,Serial No. 87,404, filed June 26, 1936. The output ill of amplifier 9is'coupled to a rectifier tube H whereof the circuit includes anode l2,cathode i3, resistances I l and I5 and inductance l6. Preferably,acapacitanoe I1 is connected in parallel with resistance It whereby thepotential drop across resistance I4 is kept at only bias value while thedrop across resistance l5 floats to change the bias on tube ll.

The high potential end of resistance I4 is connected through radiofrequency choke [8 to the cathode IQ of tube 1 and the low potential endof the same resistance is connected through radio frequency choke 2G tothe control grid of tube 1.

The cathode l3 of tube ll isconnected through a relatively highresistance 22 to a positive potential of one or two volts. The sum ofresistances M and i5 is of about the same order as is the internalimpedance of the tube II and they are divided with the ground connection23 between them. so resistance 22 will not need to be so large. Theby-pass condenser 24 is connected between choke 20 and grid 2|. Screengrid 25 of tube 1 is preferably grounded as shown and the shielding 26for lead 21 from cathode ll! of tube T to the input of receiver 8 isgrounded at 28.

Owing to the nature of the amplification effected inamplifier 9 incomingenergy of ordinary signal amplitude will not result in appreciableoutput from the amplifier 9 and therefore, due to the bias on cathode l3of tube II, the rectifier tube ll will pass no current. Consequently,when a positive voltage swing is received on plate 6 from antenna 5 thetube 1 will pass current to the receiver 8. However, when the incomingenergy has an amplitude much exceeding that of a useful signal theamplifier 9 will cause current to flow through output inductance l0 andthus will so bias the rectifier tube l I that current will flowtherethrough. It is obvious that due to the IR drop through resistance Mthe cathode I9 of tube l will have impressed upon it a positivepotential while the grid '2! thereof will have impressed upon it anegative potential, thus reducing the conductance of the tube 1 andpreventing, in proportion to the potentials impressed on cathode l9 andgrid 2|, the transfer of energy through tube I to receiver 8.

Fig. 2 shows that the envelope of the signal is superimposed upon theenvelope of the excessive amplitude disturbance but owing to the muchgreater strength of the disturbance the signal is not perceptible. Fig.3 depicts the effect of apparatus as shown in Fig. 1. It will be notedthat the first sharp rise of the disturbance is permitted to pass butthereafter the energy transmitted to the receiver 8 is substantiallyonly that of the signal wave 29. It seems probable that the passage ofthe momentary pulse of disturbance found in Fig. 3 is due to the timeconstant introduced by capacitance 24.

It is not necessary that the controlling change in conductance beexerted between the antenna and the first stage of the receiver but itmay be applied after the radio frequency to control the transfer ofenergy into the first detector input transformer and when so utilizedtuning of the amplifier 9 will be unnecessary.

Fig. 4 illustrates my'invention as applied to code reception. The tube3| is one of the radio frequency tubes in the set whereof the plate 32is coupled through capacitance 33 to plate 34 of the variableconductance tube 35. The circuit of rectifier 36 includes anode 31,cathode 38, resistance 39 and inductance 40 whereby the rectifier iscoupled to output inductance 4| of radio frequency amplifier 9, whereofthe input is connected through lead 42 to plate 32 of tube 3|. Thecathode 43 of tube 35 is connected through radio frequency choke 44 tothe high potential end of resistance 39. Control grid 45 and suppressorgrid 46 of tube 35 are connected to ground and screen grid 41 of thattube is connected to a source of positive potential.

The tube 35 now constitutes the sole connection in the signal channelbetween tube 3| and the following stage of the receiving set andconsequently any variation in the conductance of this tube is reflectedin the transfer of ener y through the signal channel. It is apparentthat the flow of current through rectifier 36 will re-- sult inimpressing a positive potential upon cathode 43 of tube 35 and thus theconductance of the tube will be reduced in proportion to the positivepotential thus applied. Since the potential drop across resistance 39depends upon fiow of current through rectifier 36 and the flow ofcurrent through the rectifier is controlled by the output of amplifier9, it is apparent that surges of energy having an amplitude above thepredetermined signal value will result in diminution of the conductanceof tube 35 to prevent transfer of the excessive amplitude energy throughthe set.

According to the provisions of the patent statutes I have set forth theprinciple and mode of operation of my invention and have illustrated anddescribed what I now consider to represent its best embodiment. However,I desire to have it understood that within the scope of the appendedclaims the invention may be practiced otherwise than as specificallyillustrated and described.

The invention herein described and claimed may be used and/ormanufactured by 01' for the Government of the United States of Americafor governmental purposes without the payment of any royalties thereonor therefor.

I claim:

1. The combination with an antenna and a radio receiver, of a vacuumtube connected in series between said antenna and the input of saidreceiver, said tube having an anode, a plurality of grids and a cathode,the said cathode only being connected to the input of said receiver, andone of said grids being grounded, a rectifier tube having an anode and acathode, an inductance and two resistances connected in series betweenthe anode and the cathode of said rectifier, a ground connection betweensaid resistances, means including an inductance connecting one end ofone of said resistances to the cathode of said vacuumtube, meansincluding an inductance connecting the other end of said one resistanceto another grid of said vacuum tube, a capacitance connecting said othergrid to ground, means to impress a positive potential upon the firstmentioned means, and radio frequency amplifying means connected to saidantenna and having an output inductance coupled with the inductancebetween the cathode and the anode of said rectifier.

2. The combination with an antenna and a radio receiver, of a vacuumtube connected in series between said antenna and the input of saidreceiver, said tube having an anode, a plurality of grids and a cathode,the said cathode only being connected to the input of said receiver andone of said grids being grounded, a rectifier tube having an anode and acathode, a resistance connected between said rectifier anode andcathode, means connecting to the cathode of said tube that end of saidresistance adjacent the rectifier cathode, means connecting the otherend of said resistance to another grid of said tube, means to impress apositive bias on the cathode of said rectifier, and amplifying meanshaving its input connected to said antenna and having its outpuconnected to said rectifier.

3. The combination with an antenna and a radio receiver, of a vacuumtube connected in series between said antenna and the input of saidreceiver, said tube having an anode, a plurality of grids and a cathode,the said cathode only being connected to the input of said receiver andone of said grids being grounded, a rectifier tube having an anode and acathode, an output circuit connecting said rectifier cathode and anode,means to apply between the cathode and another grid of said tube avoltage drop in said output circuit to diminish the conductance of saidtube in proportion to the current in said output circuit, amplifyingmeans connected to said antenna, means operatively associating saidamplifying means with said rectifier, and means to bias said rectifierto prevent appreciable output there from when the amplitude of the inputinto said rectifier is less than a predetermined value.

4. In a radio receiver, the combination with a tube connected to carrysignals in the signal channel at a frequency higher than audiofrequency, of amplifying means deriving energy from the output of saidtube, said amplifier being adapted to amplify disproportionately wavesof amplitude in excess of a predetermined value, a rectifying tubecoupled to the output of said amplifier, a resistance in the circuit ofsaid rectifier connected to the cathode of the rectifier and to ground;a pentode tube having its plate coupled to the output of the firstmentioned tube, its control grid and suppressor grid connected to groundand its screen grid connected to a source of positive potential: a radiofrequency choke connecting the high potential side of said resistance tothe cathode of said pentode, and means coupling the cathode of saidpentode to a subsequent stage in the signal channel and constitutingthesole path for energy into said subsequent stage.

5. In a radio receiver, the combination with a tube connected to carrysignal in the signal channel at a frequency higher than audio frequency,of amplifying means deriving energy from the output of said tube, arectifying tube coupled to the output of said amplifying means,resistance means in the circuit of said rectifier, a second tube havinga grid, a plate and a cathode with the said plate coupled to the outputof the first mentioned tube, means connecting the cathode of said secondtube to the high potential side of said resistance, and means couplingthe output of said second tube to a subsequent stage in the signalchannel and constituting the sole path for energy into said subsequentstage.-

6. The combination with a radio receiving system comprising a pluralityof amplification stages, of a tube having a plurality of electrodesincluding a cathode and so connected that all received energy utilizedfor signal reception must pass therethrough, said cathode only beingconnected to a subsequent stage amplifying means connected to receive aportion of the incoming energy and amplify disproportionately the excessof amplitude above a predetermined value, a rectifier coupled to theoutput of said amplifier, resistance means in the output of saidrectifier,

and means to apply the potential at the high potential point of saidresistance means to said tube to diminish the conductance of said tubeproportionately to the value of the potential at said high potentialpoint.

'7. The method of suppressing excessive amplitudes affecting receivedradio energy, which comprises the steps of collecting signal energy, di-

verting and disproportionately amplifying a portion of said energy whenexcessive amplitudes are present, rectifying said disproportionatelyamplified energy and deriving a potential therefrom, applying the saidderived potential to the remainder of said received energy beforefrequency selective transfer of said remainder to diminishproportionately to said potential the frequency selective transfer ofsaid remainder for amplification, whereby to prevent amplification ofexcessive amplitudes in said remainder, and amplifying the energytransferred.

8. The method of suppressing excessive amplitudes affecting receivedradio energ, which comprises the steps of collecting signal energy,deriving a rectified controlling potential from impulses of excessiveamplitude accompanying said signal energy, applying said potential tosaid collected energy before frequency selective transfer of said energyfor amplification to reduce the frequency selected transferred energy inaccordance with the magnitude of the applied potential, and amplifyingthe transferred energy as modified by the application of said potential.

PHILIP M. HAFFCKE.

